X11_TYPE=automatic ??

Maybe x11 detection can check more and if it really notices no X, then
continue with "modular".
If it does detect some X but not enough for x11-links then abort.
But aborting because no X installed in default pkgsrc on a Debian box is
no good if it is unattended. (I didn't realize it wanted x11-links for
my non-X package because of dependency depended on dbus. Yes I know
about PKG_OPTIONS.dbus=-x11 but that is too late.)